JP2799054B2 - Fingerprint input device - Google Patents

Description

The present invention relates to a fingerprint input device used for fingerprint collation or collation identification.

[Prior Art] In order to actually use a fingerprint as a means for personal identification, it is desirable to use a simple ink-less data input device that reduces the psychological and physical burden on the user. It is also necessary to obtain an image with good contrast between the ridges and valleys of the fingerprint.
It is necessary to have a reading accuracy of about 50 μm per pixel in consideration of the ease of subsequent processing.

Conventionally, as an input device for fingerprint recognition, a device that utilizes light emission of a substance contained in skin secretions by laser light,
There is one that uses a change in the reflected light of a finger touching a glass surface (see Fingerprint Automatic Identification Technology, Masahiro Kawagoe, Measurement and Control, Vol. 25 No. 8 pp. 701-706). Of these, the “prism method” is used in many cases. This prism method illuminates the inclined surface of the prism with total internal reflection from the inside of the glass, and forms regular reflection light on the inner surface of the glass on an image sensor with an imaging optical system outside the prism, and when inputting a fingerprint image, A finger is pressed against this slope. Then, when the finger is pressed, the skin and the glass come into contact and scatter at the convex part of the fingerprint (automatic classification of fingerprint pattern, Kawagoe, Mitsugami co-authored, IPSJ SIG Research Report, Computer Vision, 18) −2, 1982).

in this way, . Trapezoidal distortion caused by different optical paths to the image sensor for each point of the fingerprint.

. Superposition of "noise light" due to residual fingerprints of previous users. Since an optical system for image formation is required outside the prism, miniaturization is difficult in principle.

There are problems such as.

On the other hand, a method has been devised to improve the contrast by placing an image sensor in an area where scattered light does not reach (Fingerprint information detection method using a prism, Shimizu et al., IEICE National Convention, 1311, 1984) reference). A device for inputting a two-dimensional image of a ridge pattern of a fingerprint using a hologram to avoid the influence of a residual fingerprint has been devised (a personal verification device using a holographic fingerprint sensor.
Igaki et al., IEICE Research Report, Pattern Recognition and Understanding, 88-38, 1988).

However, contacting a fingerprint image with a glass surface or the like to collect the fingerprint image has the above-described problem.

[Problem to be Solved by the Invention] An input device provided with a means for making a fingerprint contact a glass surface or the like has a problem that noise light is superimposed due to a residual fingerprint of a previous user, making it difficult to extract features of the fingerprint. When a prism is used on the fingerprint contact surface, a trapezoidal distortion occurs due to a difference in the optical path to the image sensor for each point of the fingerprint, and the fingerprint image may be further distorted due to a shift in the contact position of the finger. Furthermore, since there is an individual difference in the wetness of the fingertip, the fingerprint image may become a blurred and unclear image depending on the person. Further, in order to image the fingerprint surface of the finger in a non-contact state by the finger guide, it is necessary to reliably detect the insertion of the finger into the finger guide.

Means for Solving the Problems The fingerprint input device of the present invention guides a finger to be input by a finger guide and illuminates the fingerprint surface of the finger in a non-contact state to image the finger. A mechanical switch that operates in the state of being provided is provided at the deepest part of the finger guide,
When a finger is inserted into the finger guide and the mechanical switch is depressed at the top of the finger other than the fingerprint surface, the mechanical switch is activated to detect that imaging is possible.

[Operation] When a finger is inserted along the finger guide, a mechanical switch operates to detect that the fingertip has been inserted, thereby enabling imaging. In the case of a mechanical switch, the operation is performed in a state where the finger is pushed down to the deepest part of the finger guide, so that the positional shift during imaging is reduced.

Example An example of the present invention will be described below.

FIG. 1 is a block diagram showing one embodiment of a fingerprint input device according to the present invention, which is a cylindrical finger guide 10 for inserting a fingertip.
1, an opening window 102 provided in the finger guide 101, an imaging switch 103 that operates by detecting a fingertip inserted in the finger guide 101, and receiving an imaging start signal based on the detection of the fingertip of the switch 103. A two-dimensional image sensor (for example, a CCD) 104 for picking up a fingerprint, a lens 105, a cover 106 for dustproofing the lens system, an illuminating device 107 for illuminating an assumed fingerprint surface through the opening window 102, and the imaging switch Lighting device 107 and image sensor 1 based on an input signal from 103
A CPU 108 controls the output of the imaging start signal to the image memory 04 and the writing of the captured fingerprint image to the image memory 109.

Note that the CPU 108 has a signal line with an external interface in addition to the image memory 109. Imaging switch 103 is light source 1
31, a light detector 132, and a switch 133.
OFF when in the light receiving state and ON when in the cutoff state.

The illumination device 107 uses two linear light sources such as fluorescent tubes, for example, to illuminate both sides of the pad of the finger so that the color tone of the fingerprint becomes uniform. The resolution determined by the lens 105 and the image sensor 104 is 10
It is arranged to capture at 20 pixels / mm to 20 pixels / mm.
The focal depth of the lens 105 is preferably 2 mm or more so that the fingerprint image can be clearly captured by absorbing the height difference of the fingerprint surface which is 2 mm at the maximum.

 Next, a fingerprint input operation of the above device will be described.

The subject who inputs the fingerprint image is a cylindrical finger guide 101
Along with the fingertip from the first joint to the second joint.
When the advance of the fingertip reaches a predetermined position and the fingerprint surface enters the imaging range of the two-dimensional image sensor through the opening 102, the imaging switch 103 is turned off and turned on, and the CPU 108 detects the fingertip (capturing is possible). Send a signal. CPU 108 receives the signal and outputs a lighting signal to lighting device 107. Then, the illumination lights L1 and L2 from the illumination device 107 are reflected on the fingerprint surface through the aperture window 102 provided in the finger guide 101, become reflected light L3, enter the lens 105, and generate a ridge of the fingerprint. The shading with the valley portion is formed on the two-dimensional image sensor 104 as a gray image. In that state, the two-dimensional image sensor 10
When the imaging start signal is output to 4, the fingerprint image is written to the image memory 109.

In a conventional fingerprint input device, a fingerprint surface is brought into contact with a glass surface to acquire a fingerprint image. Therefore, the image sensor is disposed with the light receiving surface facing upward. The reason for this is to make it easy to recognize the contact surface of the subject and to facilitate maintenance such as cleaning. By the way, if the light receiving surface is facing upward, the fingerprint image may be deteriorated due to the influence of noise such as dust. Therefore, in the embodiment of the present invention, the dustproof cover 106 is installed to avoid the influence of dust, and The lens system is protected from dust and other dust from parts.

On the other hand, in the fingerprint input device of the present invention, if the fingerprint surface is used as a finger guide to be inserted at an angle of 90 degrees from the upward to the left and right, and the lens surface is disposed at an angle of 90 degrees from the downward to the left and right, the dust-proof effect is further improved. Can be obtained.

FIG. 2 is a configuration diagram showing a fingerprint input device for inserting a fingerprint surface upward, wherein 201 is a finger guide, 202 is an opening window, 203 is an imaging switch, 204 is a two-dimensional image sensor, 205 is a lens, and 206 is dustproof. A cover 207 is a lighting device. With this structure, the light receiving surface of the image sensor 204 faces downward, so that it is less susceptible to dust. FIG. 3 is a block diagram showing another embodiment of the fingerprint input device of the present invention.
Denotes a finger guide, 302 denotes an opening window, and 303 denotes a push-in switch for detecting a fingertip inserted into the finger guide, and is an example of a mechanical imaging switch. The switch 303 is turned on when pressed with a finger, and sends a signal of fingertip detection (capturing is possible) to the CPU 308. 304 is a two-dimensional image sensor, 305 is a lens, 306 is a dustproof cover, 307 is a lighting device, 308 is a CPU, 309
Denotes an image memory, which is the same as the fingerprint input device of FIG. 1 except for the configuration of the image switch 303, and a description thereof will be omitted.

In this embodiment, since the mechanical push-in switch 303 is employed as the imaging switch, the fingertip is fixed at the time of imaging, and a fingerprint image with a small displacement can be obtained.

FIG. 4 is an external perspective view showing another example of the finger guide. The finger guide 401 has two tubular portions.
By inserting two fingers at the same time, the positional deviation of the fingertip in the rotation direction is prevented. That is, if two or more fingers are ergonomically inserted into the cylindrical portion, the fingers do not rotate. Reference numeral 402 denotes an opening window, on which a two-dimensional image sensor is disposed. If three or more cylindrical parts are provided, misalignment can be further prevented. In addition, an opening window is provided in each cylindrical part, and a plurality of two-dimensional image sensors are installed and multiple fingerprint images are simultaneously captured and collated in parallel. By processing, the ambiguity of fingerprint recognition can be reduced and reliability can be improved.

[Effects of the Invention] Since the fingerprint input device according to the present invention collects a fingerprint image without making contact with a glass surface or the like, it is not affected by residual fingerprints at all. Therefore, it is possible to greatly contribute to the realization of a highly recognizable device in which the influence of noise light due to stains such as residual fingerprints is minimized.

Further, the fingerprint input device of the present invention can reliably detect insertion of a finger into a finger guide.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the fingerprint input device of the present invention, FIG. 2 is a block diagram showing another embodiment of the fingerprint input device of the present invention, and FIG. FIG. 4 is an external perspective view showing an embodiment of a finger guide. Reference numerals 101, 201, 301, 401 ... finger guide, 102, 202, 302, 402 ... window, 103, 203, 303 ... imaging sensor, 104, 204, 304 ... two-dimensional image sensor, 105, 205, 305 ... lens, 106, 206, 306 ... dust cover, 107, 207, 307 ... lighting device.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G06T 1/00 A61B 5/10

Claims (1)

(57) [Claims] 1. A fingerprint input device for guiding a finger to be input by a finger guide and illuminating and imaging a fingerprint surface of the finger in a non-contact state. A fingerprint input device provided at a deepest portion of the finger input device, wherein when a finger is inserted into the finger guide and the mechanical switch is depressed at a vertex other than the fingerprint surface of the finger, the fingerprint input device is activated to detect image capture possible.